This proposal is designed to investigate the robustness of Cu-62 ETS and Positron Emission Tomography (PET) to measure myocardial blood flow in normal volunteers. This measurement is an important investigation in patients with ischemic heart disease (IHD). The importance of Cu-62 as a radionuclide relates to the convenience of using a Zinc-62 generator available for the completing of organic ligands such as PTSM. The investigators have a track record of research of myocardial perfusion in patients using Cu-PTSM. However, Cu-PTSM is not an ideal radiotracer as its myocardial uptake can be heterogenous at increased flow rates. Now we propose to compare Cu-62 ETS with Cu-62 PTSM for the measurement of coronary blood flow in human volunteers.